The invention relates to adjustable devices for anatomical support, especially cushions for the lumbar and cervical regions, to be mounted in or on the backs of seats, particularly vehicle seats, and, more particularly, to powered devices of this type for anatomical support.
Small cushions or seat backs which have some degree of adjustability are well known for lumbar and cervical support and are placed inside the seat backs of motor vehicles. The thickness and therefore outward projection can be varied to suit the needs or preferences of the user. These cushions of the prior art include a rigid structure combined with an elastic structure. Adjustment of the convexity of the elastic structure in relation to the rigid structure can be obtained by a system of cams with a tie rod. The cam can be operated from outside the seat by a mechanism including a gear wheel and worm screw and a transmission shaft worked by an external knob.
The external structure of the cushion can consist of longitudinal metal bands crossing over transversal bands with outwardly projecting ends to ensure adequate spring. This device is comparatively complex and its outer surface is rough and sharp. It must therefore be covered with a soft layer of considerable thickness. When the tie rod referred to above is part of a mechanism for changing the curvature of the elastic structure, a considerable effort is required to operate the cam. A worm screw can be used to lessen the effort involved in adjusting the device, but the adjusting knob must be given a great many turns so that the adjustment time is far too long.
Some of the above-described prior art devices which adjust the seat back convexity cannot be moved vertically from the lumbar to the cervical region or in between, or adapted to the stature, needs and preferences of the user.
These drawbacks lessen the advantages of these devices not only because of their cost, but also for practical reasons and duration.